1. Field of the Invention
The present invention relates to a nitride semiconductor light emitting device, and more particularly to a nitride semiconductor light emitting device including a light emitting diode and a diode that are formed on a single substrate, which allows the light emitting diode and the diode to use a common electrode, so that it prevents the light emitting diode from being damaged by static electricity, and reduces the size of an overall device and the number of necessary electrodes.
2. Description of the Related Art
In recent times, nitride semiconductors have been introduced, which use a nitride such as GaN, and have excellent physical and chemical characteristics so that they are increasingly popular as a core material of a photoelectric or electronic element. Particularly, the nitride semiconductor light emitting diode is capable of emitting light of a variety of wavelengths, for example, green, blue, and ultraviolet. As individual brightness of the above-mentioned light wavelengths is rapidly increased due to the increasing development of associated technology, nitride semiconductor light emitting diodes have recently been applied to a variety of technical fields, for example, natural-colored electronic display boards and illumination systems, etc.
The nitride semiconductor light emitting diode has a disadvantage in that it has very weak resistance to static electricity as compared to other compound semiconductors such as GaP or GaAlAs. For example, the nitride semiconductor light emitting diode may be damaged by a forward constant voltage of several hundreds of volts (e.g., 100V), and may also be damaged by a reverse constant voltage of several tens of volts (e.g., 30V). Nitride semiconductor light emitting diodes are very vulnerable to the above-mentioned constant-voltages and may be damaged thereby when they are handled. Therefore, many developers have conducted intensive research into a variety of technologies capable of obviating the above-mentioned problem of the nitride semiconductor light emitting diode. A representative example of such technologies has been disclosed in U.S. Pat. No. 6,593,597, entitled “GROUP III–V ELEMENT-BASED LED ESD PROTECTION CAPACITY”, by South Epitaxy Corporation, which is incorporated herein by reference. The U.S. Pat. No. 6,593,597 shows a nitride semiconductor light emitting device in which a light emitting diode and a diode are simultaneously formed on a single substrate.
FIG. 1 is a cross-sectional view illustrating a light emitting diode (LED) shown in the above-mentioned U.S. Pat. No. 6,593,597. As shown in FIG. 1, the conventional LED 10 for preventing static electricity from being generated (hereinafter referred to as an electrostatic discharge (ESD) protection diode) forms an LED unit A and a diode unit B on a single substrate. The LED unit A sequentially forms a buffer layer 12, an n-type nitride semiconductor layer 13a, an active layer 14, a p-type nitride semiconductor layer 15 on a substrate 11. A p-type electrode 16a is formed on the p-type nitride semiconductor layer 15. An n-type electrode 16b is formed on the exposed n-type nitride semiconductor layer 13a. The diode unit B forms two electrodes 17a and 17b on the n-type nitride semiconductor layer 13b, and allows a single electrode 17a of said two electrodes 17a and 17b to form a Schottky contact with the n-type nitride semiconductor layer, such that a Schottky diode is implemented.
The above-mentioned electrostatic discharge (ESD) protection LED 10 implements each of the LED unit A and the diode B on the substrate 11, such that it has a disadvantage in that it unavoidably increases its own overall size as compared to the size of a general nitride semiconductor light emitting device.
The LED unit A requires two electrodes 16a and 16b to provide an electrical connection, and the diode unit B requires two electrodes 17a and 17b to provide an electrical connection, such that the number of electrodes is unavoidably increased, and each electrode must require wire bonding when being connected to an external circuit. Indeed, the nitride semiconductor light emitting diode has a very small size, so that the wire bonding of each electrode is considered to be very difficult. Four wire bonding processes must be carried out in a narrow area, such that a short-circuit may unexpectedly occur between individual wires.
The above-mentioned electrostatic discharge (ESD) protection LED 10 has a further disadvantage in that all the four lead patterns respectively connected to terminals must be formed on a single submount in the case of using a flipchip-structured light emitting device.